This disclosure relates to fan inlet diffuser housings, and more particularly, fan inlet diffuser housings for air cycle machine systems.
Typically, in modern commercial aircraft, an air cycle machine (ACM) is provided to suitably condition air to be supplied to the cabin or cockpit or other locations for occupant comfort. An air cycle machine system includes a fan inlet diffuser housing to receive the flow of intake air drawn in by the air cycle machine. A flow path of the air cycle machine system can include a heat exchanger cooling flow that draws air through a heat exchanger, past a fan rotor, and dumps the flow into an overboard duct. The fan rotor can be used to establish the flow when insufficient ram air is available to draw air through the heat exchanger. While in service, the heat exchanger can become partially clogged due to dust or other contaminants that reduce available flow volume to the fan rotor, which pushes the fan rotor closer to its surge limit. Designs that attempt to enhance flow as the fan rotor approaches its surge limit may experience a reduction in performance when operating under off-design conditions, which can reduce tolerance to heat exchanger blockage. A unique airflow path shape is needed to meet system performance requirements and to allow efficient fan flow recirculation if the heat exchanger becomes clogged. Further, reducing weight for aerospace applications, while selectively establishing regions of increased structural integrity, can present a number of challenges.